Revisiting the cerebral hemodynamics of awake, freely moving rats with repeated ketamine self-administration using a miniature photoacoustic imaging system.

Significance: Revealing the dynamic associations between brain functions and behaviors is a significant challenge in neurotechnology, especially for awake subjects. Imaging cerebral hemodynamics in awake animal models is important because the collected data more realistically reflect human disease states. Aim: We previously reported a miniature head-mounted scanning photoacoustic imaging (hmPAI) system. In the present study, we utilized this system to investigate the effects of ketamine on the cerebral hemodynamics of normal rats and rats subjected to prolonged ketamine self-administration. Approach: The cortical superior sagittal sinus (SSS) was continuously monitored. The full-width at half-maximum (FWHM) of the photoacoustic (PA) A-line signal was used as an indicator of the SSS diameter, and the number of pixels in PA B-scan images was used to investigate changes in the cerebral blood volume (CBV). Results: We observed a significantly higher FWHM (blood vessel diameter) and CBV in normal rats injected with ketamine than in normal rats injected with saline. For rats subjected to prolonged ketamine self-administration, no significant changes in either the blood vessel diameter or CBV were observed. Conclusions: The lack of significant change in prolonged ketamine-exposed rats was potentially due to an increased ketamine tolerance. Our device can reliably detect changes in the dilation of cortical blood vessels and the CBV. This study validates the utility of the developed hmPAI system in an awake, freely moving rat model for behavioral, cognitive, and preclinical cerebral disease studies.

Clinical Disease Severity Mediates the Relationship between Stride Length and Speed and the Risk of Falling in Parkinson's Disease.

The shuffling gait with slowed speed and reduced stride length has been considered classic clinical features in idiopathic Parkinson's disease (PD), and the risk of falling increases as the disease progresses. This raises the possibility that clinical disease severity might mediate the relationship between stride length and speed and the risk of falling in patients with PD. Sixty-one patients with PD patients underwent the clinical scores as well as quantitative biomechanical measures during walking cycles before and after dopamine replacement therapy. Mediation analysis tests whether the direct effect of an independent variable (stride length and speed) on a dependent variable (three-step fall prediction model score) can be explained by the indirect influence of the mediating variable (Unified Parkinson's Disease Rating Scale (UPDRS) total scores). The results demonstrate that decreased stride length, straight walking speed, and turning speed is associated with increased three-step fall prediction model score (r = -0.583, p < 0.0001, r = -0.519, p < 0.0001, and r = -0.462, p < 0.0001, respectively). We further discovered that UPDRS total scores value is negatively correlated with stride length, straight walking, and turning speed (r = -0.651, p < 0.0001, r = -0.555, p < 0.0001, and r = -0.372, p = 0.005, respectively) but positively correlated with the fall prediction model score value (r = 0.527, p < 0.0001). Further mediation analysis shows that the UPDRS total score values serve as mediators between lower stride length, straight walking, and turning speed and higher fall prediction model score values. Our results highlighted the relationship among stride length and speed, clinical disease severity, and risk of falling. As decreased stride length and speed are hallmarks of falls, monitoring the changes of quantitative biomechanical measures along with the use of wearable technology in a longitudinal study can provide a scientific basis for pharmacology, rehabilitation programs, and selecting high-risk candidates for surgical treatment to reduce future fall risk.

Extending Absorption Edge through the Hybrid Resonator-Based Absorber with Wideband and Near-Perfect Absorption in Visible Region.

Metamaterial absorber with the unexpected capability for harvesting electromagnetic energy has been regarded as a potential route for various applications, including chemical/biological sensing, cloaking and photovoltaic applications. In this study, we presented the simple absorber design made with Al/SiO2/Al sandwich structures through the involvement of hybrid dual-resonators that could allow the wideband light absorption covered from 450 nm to 600 nm with average absorptivity above 95%. Examinations of excited electric field, magnetic field and total magnitude of electric field in three-dimensional space at resonances were performed to clarify the origin of resonant behaviors. In addition, an equivalent inductance-capacitance circuit model was proposed that could qualitatively explore the geometry-dependent absorption characteristics by modulating the constitutive parameters of hybrid resonators. As a result, the designed light absorber might enable to be practically applied for various optical-management and photovoltaic applications, and even offered the tunability for other desired frequency regions.

Plasmonic mode converter for controlling optical impedance and nanoscale light-matter interaction.

To enable multiple functions of plasmonic nanocircuits, it is of key importance to control the propagation properties and the modal distribution of the guided optical modes such that their impedance matches to that of nearby quantum systems and desired light-matter interaction can be achieved. Here, we present efficient mode converters for manipulating guided modes on a plasmonic two-wire transmission line. The mode conversion is achieved through varying the path length, wire cross section and the surrounding index of refraction. Instead of pure optical interference, strong near-field coupling of surface plasmons results in great momentum splitting and modal profile variation. We theoretically demonstrate control over nanoantenna radiation and discuss the possibility to enhance nanoscale light-matter interaction. The proposed converter may find applications in surface plasmon amplification, index sensing and enhanced nanoscale spectroscopy.

A comparative study of gold nanocubes, octahedra, and rhombic dodecahedra as highly sensitive SERS substrates.

Gold nanocubes, octahedra, and rhombic dodecahedra with roughly two sets of particle sizes have been successfully synthesized via a seed-mediated growth approach. All six samples were analyzed for comparative surface-enhanced Raman scattering (SERS) activity. All of these Au nanostructures were found to yield strong enhancement at a thiophenol concentration of 10(-7) M and are excellent SERS substrates. Rhombic dodecahedra with a rhombus edge length of 32 nm showed significantly better enhancement than the other samples and can reach a detection limit of 10(-8) M. Simulations of the binding energies of thiophenol on the different faces of gold and electric near-field intensities of these nanocrystals have been performed to evaluate the experimental results. Superior SERS activity of these nanocrystals can be expected toward the detection of many other molecules.

Tissue-specific differences in mitochondrial DNA content in type 2 diabetes.

BACKGROUND: To investigate whether the effect of hyperglycemia on mitochondrial DNA (mtDNA) content is tissue-specific. METHOD: We compared the mtDNA contents in leg muscle, blood vessel, and peripheral leucocytes in seventeen patients with type 2 diabetes (T2DM) with those of seven controls. We measured 8-hydroxydeoxyguanosine (8-OHdG) expression in the muscles and thiobarbituric acid reactive substance (TBARS) in sera to evaluate oxidative stress. Immunohistochemical detection of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC1-α), mitochondrial transcription factor A (Tfam), and apoptosis were performed in the muscle tissue. RESULTS: The mtDNA copy number was highest in muscle tissue, followed by blood vessel tissue, and lowest in leucocytes in both the diabetic and control subjects. The diabetic patients had less mtDNA content in the muscle than the controls (2.86±0.33 vs. 3.20±0.14, P=0.025), but more mtDNA content in the leucocytes (2.25±0.26 vs. 1.98±0.06, P=0.04). In both groups, there was a positive correlation between muscle tissue mtDNA content and the expression of 8-OHdG. Patients with T2DM had significantly increased 8-OHdG and TUNEL labeling index and non-significant increases in the expression of PGC1-α and Tfam. CONCLUSION: Oxidative stress stimulates mitochondrial biogenesis but induces a greater degree of apoptosis in diabetic patients, resulting in a decrease in muscle tissue mtDNA content.